The present invention relates to novel pyrimidine derivatives and to the use of such derivatives and related compounds to inhibit sorbitol dehydrogenase (SDH), lower fructose levels, or treat or prevent diabetic complications such as diabetic neuropathy, diabetic retinopathy, diabetic nephropathy, diabetic cardiomyopathy, diabetic microangiopathy and diabetic macroangiopathy in mammals. This invention also relates to pharmaceutical compositions containing such pyrimidine derivatives and related compounds. This invention also relates to pharmaceutical compositions comprising a combination of a sorbitol dehydrogenase inhibitor of formula I and an aldose reductase inhibitor and to the use of such compositions to treat or prevent diabetic complications in mammals. This invention also relates to pharmaceutical compositions comprising a combination of a sorbitol dehydrogenase inhibitor of formula I and an NHE-1 inhibitor and to the use of such compositions to reduce tissue damage resulting from ischemia, and particularly to prevent perioperative myocardial ischemic injury.
S. Ao et al., Metabolism, 40, 77-87 (1991) have shown that significant functional improvement in the nerves of diabetic rats (based on nerve conduction velocity) occurs when nerve fructose levels are pharmacologically lowered, and that such improvement correlates more closely with the lowering of nerve fructose than the lowering of nerve sorbitol. Similar results were reported by N. E. Cameron and M. A. Cotter, Diabetic Medicine, 8, Suppl. 1, 35A-36A (1991). In both of these cases, lowering of nerve fructose was achieved using relatively high does of aldose reductase inhibitors, which inhibit the formation of sorbitol, a precursor of fructose, from glucose via the enzyme aldose reductase.
U.S. Pat. Nos. 5,138,058 and 5,215,990, which are hereby incorporated by reference, each disclose compounds of the formula                 where R1, R2, R3, R4 and R5 are as disclosed therein. Said compounds are disclosed as having utility as tools in screening for aldose reductase inhibitors due to the sorbitol accumulating activity of said compounds.        
Commonly assigned U.S. Pat. Nos. 5,728,704 and 5,866,578, which are hereby incorporated by reference, each disclose compounds of the formula A, wherein R1 through R5 are defined as disclosed therein. Further, U.S. Pat. No. 5,728,704 discloses that sorbitol dehydrogenase compounds have utility in the treatment of diabetic complications.
Pyrimidine derivatives of the formula I, as defined below, and their pharmaceutically acceptable salts, lower fructose levels in the tissues of mammals affected by diabetes (e.g., nerve, kidney and retina tissue) and are useful in the treatment and prevention of the diabetic complications referred to above. These compounds, or their metabolites in vivo, are inhibitors of the enzyme sorbitol dehydrogenase, which catalyzes the oxidation of sorbitol to fructose.